[未归类] Nanyang PhD Opportunity [复制链接]

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电梯直达

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发表于 2010-4-26 18:31:41 |只看该作者 |倒序浏览

Dr Dan Zhao is looking for high-calibre PhD students to start in August 2010. Full scholarship is available for qualified candidates.
The research topics include:
1.
Active/passive control of combustion instabilities
The drive for reducing NOx emissions and improving combustion efficiencies means that many gas turbines and aero-engines are being operated under lean premixed conditions. This makes them particularly susceptible to combustion instabilities, which are characterized by large combustion oscillations. The self-excited pressure oscillations may become so intense that they may cause structural damage and costly mission failure. Combustion instability is currently a major challenge for industrial gas turbine and next generation of aero-engines manufacturers.
To eliminate combustion instabilities, either active or passive control can be implemented. Active control techniques involve a control system and use a dynamic actuator such as a loudspeaker or fuel supply valve. The actuator ‘perturbs’ the state of the combustion system according to measurements to interrupt the coupling between the pressure and the heat release. If the way in which the actuator driven by a controller responds to the measurements has been designed incorrectly, the system won’t be stabilised. Thus, designing a robust and efficient controller plays an important role in stabilizing combustion systems. Passive control techniques generally add acoustic damping to the combustion system by introducing acoustic dampers. Their damping mechanism is primarily due to the thermo-viscous and vortex shedding losses. Acoustic dampers such as Helmholtz resonators and perforated liners have been widely used in aero-engines and gas turbines, since they are unlikely to make the system more unstable. However, such dampers tend to be effective only over a narrow frequency range and are unable to respond to changes in operating conditions.
Currently, more systematic approaches such as actively passive control and adaptive control are now being promoted so that the range at which combustion systems operate stably is broadly extended. Dan Zhao is developing control algorithms for actively tuning acoustic dampers, and adaptive controller to stabilize combustion systems. He is also interested in active/adaptive noise/flow control.
2.
Real-time flow measurement using noise logging technique
The use of an array of sensors for determining the properties of propagating acoustic waves is considerably important in many application areas, such as in radar and sonar system. The present work will be concerned with the use of an array of sensors to determine the flow rate of oil/gas pipelines. In particular, the emphasis will be on the real-time application based on online pressure measurement acquired by the distributed acoustic sensors.
It is known that the fluid flowing through restricted channels, leaks and perforations can generate characteristic sound. With proper diagnosis approaches (algorithms), the sound can be used to determine the flow properties, such as speed of sound and flow rate. Dan Zhao is developing simple but robust algorithms to determine flow properties.
He is also interested in acoustic imaging techniques and multi-dimensional spectral estimation.
Further details may be obtained from Dr D. Zhao (Tel: +65 6790 4442 email: zhaodan@ntu.edu.sg). Only the short-listed candidates will be contacted. A formal application for admission should be sent to Nanyang Technological University. Information and forms can be found from the website: http://www3.ntu.edu.sg/mae/Academic/PStudent/MengPhd/Application.asp
Closing date: 07 May. 2010. Planned interview dates: Interviews will be held with selected candidates as soon as possible after the closing date.

港科的电信学和KTH的嵌入式系统，怎么选？